The KwakiutI recognized one social unit larger than the tribe-the confederacy, which was a cluster of loosely knit, informally related neighboring tribes who interacted with themselves more often than between other tribes.

A. tribes who interacted with themselves more often than between

B. tribes who interacted among each other more often than among

C. tribes who interacted with one another more often than with

D. tribes, interacting among each other more often than between

E. tribes, interacting among one another more often than with

i have following questions :
question 1 : is it true that when two or more than two adjectives describe the same noun then those adjectives can be separated by commas?
as has been done here :which was a cluster of loosely knit, informally related neighboring tribes
i very faintly remember having read this rule some where in RON's post but cannot find it now so plz kindly confirm this rule .

my second question : when 2 people are there is it rite to say : they interact with each other
however when more than 2 people are there then its wise to say : ....interact with one another

my third question : also if we want to use "among" for showing interaction then we sud be saying : they interact among themselves (reflexive pronoun)

instructors plz help
thanks and regards